1. Field of the Invention
The present invention relates generally to the field of archery and, more specifically, to a nock system capable of selectively securing a nock into the nock end of a hollow arrow shaft.
2. Related Applications
This application is a continuation-in-part of copending application Ser. No. 08/180,220, entitled "Dual-Purpose Arrow Shaft Insert," filed Jan. 1, 1994, in the name of Louis Rangel.
3. Background Art
Archery has served to provide sustenance and recreation since prehistoric times. Today, however, the carved wooden arrows of the past have been replaced by highly refined arrows made of light-weight, high-strength alloys and composites.
Modern arrow shafts are hollow and made of aluminum, fiberglass, graphite, or carbon materials. Attached to the leading end or point end of the shaft is a point. Radially extending near the opposing or nock end of the shaft are fletchings or vanes which give the shaft stability in flight. The fletching comprises a plurality of equally spaced extensions made of feathers or synthetic materials. Secured to the trailing end or nock end of the shaft is a nock for receiving the bow string. While refinement of the arrow has improved accuracy, improvements have also wrought problems.
For example, to attach the nock, the majority of arrows utilize a glue-in insert from which projects a swage. A nock having a hollow end corresponding in size and shape to the swage is then glued over the swage and permanently bonded. The problem with this system, however, is that the nock cannot be rotated or "indexed" after it is glued onto the swage. Nocks must be rotated or "indexed" with respect to the nock insert in order to obtain optimum flight characteristics when the arrow is released from the bow. During passage of the arrow over an arrow rest, portions of the fletching of the arrow come in contact with the arrow rest. By indexing the nock, the contact between the fletching and the arrow rest of the bow can be minimized to reduce the affect of the contact on the flight path of the arrow.
An additional problem with having the nock glued to the swage is that it is difficult to remove and replace the nock. In archery competitions, an arrow will often strike a previously lodged arrow and deform or break the nock of that arrow. In order to reuse the arrow shaft, it is desirable to be able to quickly remove the broken nock and replace it with a new one. This is difficult when the nock is glued to the swage.
To overcome these problems, tubular inserts having a receiving chamber have been developed. The insert is secured (typically glued) into the arrow shaft. A nock having a shank with a diameter complementary to the receiving chamber is then press-fit into the insert. Using this system, a nock is capable of being indexed by rotating the nock to overcome the friction between the nock and the insert. Although this system overcomes some problems, additional drawbacks are encountered.
When the nock is inserted into the arrow shaft, even slight variations in the longitudinal axis of the nock in relation to the longitudinal axis of the arrow shaft can result in an inaccurate flight path. Because of the substantial impact which the point of a modern arrow undergoes due to higher flight speeds, vibration from the impact travels through the shaft and into the nock insert causing the nock to work loose. As the nock vibrates loose, the nock may alter the flight path of the arrow during subsequent flights.
Furthermore, since the nock is only secured to the hock insert by frictional forces resulting from press fitting, vibrations, indexing, and replacing of the nock can wear down the shaft of the nock resulting in the nock being loosely fitted. As such, the nock can be easily misaligned and thereby affect the flight path of the arrow.
As an additional limitation, nock inserts capable of receiving press-fit nocks do not have any internal surfaces which can easily be gripped to remove the nock insert from the shaft. Archers wishing to salvage nock inserts from damaged arrows must attempt to remove the nock insert by heating the glue and removing the insert from the heated arrow with pliers. Unfortunately, the pressure required to remove the nock insert often results in deformation of the nock insert and shaft due to the pressure which must be applied by the pliers.
The current adhesive systems for attaching the insert to the arrow shaft are also cumbersome. The user must heat a heat-sensitive adhesive stick and then paint the adhesive onto the insert prior to pressing the insert into the arrow shaft. Typically, a portion of the glue or adhesive is scraped off as the insert is pressed into the arrow shaft. This results in uneven application of the adhesive and premature failure of the joint.
To increase the accuracy of an arrow, archers also consider the weight balance and type of fletching. For example, if the fletching on an arrow is changed from feathers to plastic vanes, the balance of the arrow will be altered by the heavier plastic vanes. The weight of the point and the nock insert will also affect the balance of the arrow. Although some bias toward the front of the arrow is desirable, too much bias in that direction may result in an arrow which has an erratic flight path.
During competition, the similarity of nock colors and fletching may make it difficult to determine which arrows belong to which competitor. It becomes important to distinguish arrows when adjustments to the trajectory of subsequent shots is desired. This can be overcome by changing the nock in the arrow to a distinctive color. Archers in competitions are hesitant to change nocks, however, because of the chance that a replacement nock will not seat properly and will upset the trajectory of the arrow.